1. Field of the Invention
The present invention relates to an oil pump for an internal combustion engine. More particularly it relates to an improved gerotor gear oil pump for use with a motorcycle engine employing a dry sump lubrication system and providing an improved design and ratio of scavenging pump capacity to engine supply side capacity. The design provides both improved performance and lubrication for the motorcycle engine and a gain in net horsepower in such an engine despite the use of increased gear size which would normally cause a decrease in net horsepower of the engine. Additionally, the modular design of the preferred embodiment provides the ability to assemble an oil pump with two or more pumping chambers into a single pump unit that is customizable to the required performance characteristics of the motorcycle for the type of riding intended.
In a preferred embodiment, the device features a multiple piece formed pump unit having a pressure pump housing and a scavenge pump housing separated by a separator plate and which are configured for cooperative sealed engagement in line and adjacent to each other to thereby house the rotating gerotor gears housed internally in each separate housing making up the pump housing. An outer wear plate, or sidewall formed by the engine to which the pump unit attaches defines the outer wall of a pressure chamber formed by the pump housing and the separator plate. The device also features the gears of the scavenge pump portion sized to specific pumping volume ratios in relation to the gears in the pressure pump portion to scavenge oil and gas pressure from the engine at a ratio sufficient to minimize windage and drag caused by oil occupying one or a plurality of sumps in the engine by draining such oil to a fluid reservoir supplying the pressure pump before it encumbers the rotation of internal engine components. Concurrently the scavenge pump portion, when in a correct ratio to the pressure pump fluid pumping capacity, ensures that the pressure pump is provided with a constant and uninterrupted supply of lubrication fluid from the fluid reservoir which can be delivered to engine components by the pressure pump during all phases of engine operation from idle to high RPM long duration operation.
The multi-piece design also allows the pump to be manufactured and sold as a kit which features cooperating pump gears and scavenge gears and pump housings and scavenge housings that are sized at different ratios in relation to each other. In this fashion the ratio of fluid volume pumped from the sumps by the scavenge pump in relation to the oil pumped by the pressure pump portion may be adjusted by using different sized gears and different sized engageable housing components. The chosen gears and housings form the two separate pumps which may then be assembled into a custom oil pump with the separator plate and the end plate or an engine wall as the case may be, with the desired ratio of scavenge pump volume to pressure pump volume to fit the intended use of the motorcycle.
2. Prior Art
Motorcycle engines in prior art generally employ a lubrication system that uses either a dry sump or wet sump. In both such wet sump and dry sump lubrication systems, the lubrication fluid, most commonly motor oil, collects in a sump at the bottom of the crankcase after the oil has been pumped to and lubricated various components of the engine. In a wet sump lubrication system, using a single oil pump, the oil is generally pumped directly from the crankcase sump or other sumps formed in the engine case, to the components of the engine requiring lubrication. In a dry sump lubrication system, the oil that collects in the engine sump, is pumped out of the crankcase sump by a first pump, which delivers the oil to a reservoir. Oil stored in the reservoir is then communicated via conduits to a second or pressure pump which pumps it to the parts of the engine requiring oil during operation through communicating conduits.
Gerotor oil pumps are well known in the art for pumping fluids and available from many sources such as Nichols Portland of Portland, Me. and Federal Mogul of Detroit, Mich. The theoretical flow ripple of the fluid pumped by gerotor pumps depends on the number of teeth in the pump gears and the specific geometry of the gerotor but in general more teeth means a lower flow ripple. Additionally, an inner gerotor gear with an even number of teeth typically has a lower fluid flow ripple than an inner gear having an odd number of teeth.
Since hydraulic power is a function of flow and pressure, the mechanical energy losses to the driving engine generally are caused by the viscous drag on the gears being driven. Consequently the gerotor with the smallest outside diameter will generally cause the lowest power loss to an engine driving it due to the developed viscous drag. Additionally smaller gears minimize vibration. Increasing gear size would generally be expected to cause a concurrent decrease in the net available horsepower of the engine driving the pump, since viscous drag is increased from the increased pumping and more horsepower is then required to power the pump. As such, engine manufacturers generally minimize the size of the gears to minimize vibration and power loss from the engine required to power them.
U.S. Pat. No. 6,047,667 (Leppanen) discloses an oil lubrication system using a gerotor pump for use in a motorcycle engine. However, Leppanen teaches the use of a one piece casing housing two adjacent pump gears and fails to teach any benefits derived from the critical ratio of the scavenging gear and resulting pumping volume to the pressure gear and resulting pressure pumping volume. Neither does Leppanen provide any ability to assemble pumps and adjust ratios of the scavenge and pressure section by the use of different components from a kit of different sized scavenge and pressure gears and casings all of which may easily be assembled into a functioning pump with optimum dimensions and ratios.
U.S. Pat. No. 6,116,205 (Troxler) also teaches the use of a gerotor oil pump for a motorcycle engine to drain two different sumps. The use of such a pump to simultaneously drain two different sumps on an engine, and pressurize oil passages on that engine is well known art in lubrication systems for internal combustion engines including motorcycles and automobiles. Troxler teaches the use of a one piece pump housing which is not designed to allow gear ratio adjustments and fails to teach any benefit from such adjustments or increasing the volume pumping size of the pumps. Neither does Troxler make any accommodation to the gear mounting on the drive shaft to allow for wear or end play which might cause the gears to bind with the body or endwalls when the pump is assembled.
As such, there is a pressing need for an oil pump with separate housings and separate scavenging and pressurizing chambers therein which may be specifically sized such that the ratio of the scavenging gears to the pressurizing gears is optimized to vent fluids from the engine sumps at an optimum rate during all operation speeds. Such a device should allow for maximum lubrication by the oil pressurizing pump at all engine speeds and optimize removal of oil and internal gas pressure from the sumps to minimize windage and interference by fluids in the sumps with the rotating mechanical components of the engine.
Still further, such a device when assembled from a plurality of different pump components into a single pump unit would offer the further benefit of the ability to choose specific gearing matched to specific assembleable housings or casings to form the two-chambered pump. By the careful selection of the fluid pumping volume of the scavenge portion of the formed pump to the pumping volume of the pressurizing portion, from a plurality of configurable casings and gears designed to interface and assemble to a pump, manufacturers, distributors, and users, can assemble a properly sized and proportioned pump with the optimum ratio of volume of the scavenging pump to the pressurizing pump to maximize both lubrication and net horsepower to each individual engine and the expected operating parameters of that engine. Additionally, by providing a means to accommodate end play and/or an out of tolerance mounting of the gears on the drive shaft, such a system would eliminate potential binding of the gears on the pump casings when the pumps are assembled and used.
Applicant""s device is an improved two chambered gerotor oil pump for use on internal combustion engines. The preferred embodiments of the device, for use on a dry sump style engine, feature a scavenging pump chamber formed in a scavenging housing and further defined by a sidewall opposite a separator plate, and, an inline pressure pump chamber formed in a pressure housing and further defined by a separator plate between it and the scavenging pump and an opposing end wall. Gerotor gears operatively occupy both the scavenging pump chamber and the pressure pump chamber and are both situated for inline mounting on a driving shaft communicating axially through the center portion of both chambers. In some instances the sidewall of the scavenging chamber or exterior wall of the pressure chamber may be provided by mounting the assembled pump housings to the engine block or factory end plates or both the sidewall and the exterior wall may be provided as parts for use in with the assembled pump assembly to maintain tolerances between the parts.
In use in the current best embodiment the improved oil pump would be assembled from the various components to yield a pump for both scavenging lubricating fluids from one or a plurality of engine sumps and pumping such lubricating fluids for the engine used in combination herewith which has the best ratio of gear sizing to yield the pumping volume for the intended engine and the use of the intended engine. For example motorcycles for competition tend to reach high engine speeds and to constantly accelerate and decelerate such engine speeds. Conversely, street and highway driven motorcycles tend to accelerate less and to shift to higher gears for long periods of riding at highway speeds with constant but lower RPM than those encountered by racing motorcycles.
It is an object of this invention to provide an oil pump for internal combustion engines, especially motorcycles, which ratios the pumping volume of the scavenge pump to the pumping volume of the pressure pump, to maximize performance and minimize power loss.
Another objective of this invention is to provide such a multi chambered oil pump which is assembled from modular components allowing for the adjustment of gear sizes in each respective pump section to achieve the best size and ratio of pumping volume therebetween for the intended installation of the pump.
An additional objective of this invention is to provide a multi chambered oil pump which is assembled from modular components allowing for the easy replacement and repair of the assembled pump components.
A still further object of this invention is the provision of an oil pump with a scavenging pump to pressure pump pumping volume ratio which minimizes or eliminates horsepower loss to the driving engine by removing excess liquid and gas from the engine sumps which interfere with mechanical movement, while providing an adequate supply of lubrication fluid to a reservoir and communicating pressure pump for engine lubrication purposes.
Further objectives of this invention will be brought out in the following part of the specification, wherein detailed description is for the purpose of fully disclosing the invention without placing limitations thereon.